xperime 

 all valu 



26 H. A. Rowland — Studies on Magnetic Distribution. 



The observations in Table XL are the mean of four observa- 

 tions made on both ends of the bar and with the current in 

 both directions. 



The agreement with the formula in this table is quite good ; 

 but we still observe the excess of observation over the formula 

 at the end, as we have done all along. Here, for the first time 

 we see the error introduced by the method of exp 

 I have before referred to in the apparently g 

 ata:=-75. 



On trying the steel bar, I came across a curious fact which, 

 however, I have since found has been noticed by others. It is 

 that when an iron or steel bar has been magnetized for a long 

 time in one direction and is then demagnetized, it is easier to 

 magnetize it again in the same direction than in the opposite 

 direction. The rod which I used in this experiment bad been 

 used as a permanent magnet for about a month, but was demag- 

 netized before use. From this rod five cases of distribution 

 were observed : first, when the bar was used as an electro-mag- 

 net with the magnetization in same direction as the original 

 magnetism; second, ditto with magnetization contrary to orig- 

 inal magnetism ; third, when used as a permanent magnet with 

 magnetism the same as the original magnetism ; fourth, ditto 

 with magnetism opposite; and fifth, same as third but curve 

 taken after several days. The permanent magnetism was 

 given bv the current. 











Tablk XII. 



Stub's 



Steel. 









Electro-magnet. 



Permanent magnet. 





Ir^nl 



SI-: 



Original. 



Ma^etism 



S- 



Ditto third 

 After three or 

 four days. 





Q^. 



447r^. 



Q.. 



47rA. 



Q.. 



nl. 



Qe. 



AnX. 



Q..].-. 



t 



'23-3 



23-0 



1 



1 





'i 



5-3 



^•9 



I 



2-9 2-9 



The observations in Tables XI and XII. can be compared 

 together, the quantities being expressed in the same unknown 

 arbitrary unit. It is to be noted that the bars in Tables XL 

 and XII. were subjected to the same raagnetizing-force. 



